Disconnected from the game after 00:00:01.

[Atsilieri]

Hello, this is my first post, so I would like to say a warm hello to all you great people, who created and manage eurobattle.net.
Now my problem is this:
I set up my favorite Quick Game settings (Human, 1v1) and then press "Play" to get into a game. I usually find a game within 15 seconds. Now as I finish loading (and most of the times wait for the other player to finish loading), I get into the game. I see my 5 peaceful Peasants standing there, I click one of them and issue the move order, but nothing happens. Instead, a blink later the game throws a "You were disconnected" notice to me.
Now I tried
1) Disabling my Firewall
2) Allowing ports and war.exe + euroloader.exe through the firewall.

None of them helped. I have a TP-Link WL-542G (something like that) router.
But why should the router stop me from playing? I am not hosting a server, or am I?
I can play on Custom Games just fine, with someone else hosting (haven't tried hosting myself, cause I don't have the internet for it).
I just want to play normal Warcraft III TFT online, not some Fooooootmen or DotA mumbo-jumbo.
Thanks for reading and I'd be grateful for any hints or tips, that might help me.